1. Field of the Invention
This invention relates to a diffusion transfer type duplicating camera used for the preparation of a block copy.
2. Description of the Prior Art
In this diffusion transfer type duplicating camera, a photosensitive material, called a negative paper, is exposed to light to obtain a latent image of an original on the photosensitive material. This exposed photosensitive material is then superimposed on an image receiving material, called a positive paper, and these materials are then immersed in a developer, so that the image recorded on the photosensitive material is diffused and transferred to the image receiving material. To obtain a latent image on the photosensitive material, it is necessary for a type of a duplicating camera, which takes an image of an original, to be capable of correctly acquiring images from a large A3 size original, or thereabouts, without distortions. Examples of such diffusion transfer type duplicating cameras are disclosed in Japanese Unexamined Utility Model Publication No. 62(1987)-6735, Japanese unexamined Patent Publication No. 1(1989)-112242, and Japanese Patent Publication No. 64(1989)-7648. These duplicating cameras also have drawbacks in that they become significantly bulky and heavy because of their reducing and magnifying functions.
For these reasons, when the duplicating camera is arranged such that the surface of the original, situated on a transparent glass original table, is scanned from the below thereof by means of a scanning unit including a light source which scans in the pattern of a slit, and that the light reflected from the original is radiated through a lens onto a sheet-like photosensitive material to be carried, the duplicating camera can have a simpler structure, and be made smaller so it becomes possible to carry out duplication like copying. By virtue of its reducing and magnifying functions, it is possible to change the ratio of the optical path length between the original and the lens to the optical path length between the lens and the photosensitive material, and also possible to adjust the ratio of the scan speed of the scanning unit to the feeding speed of the photosensitive material.
This duplicating camera is usually made up of an exposure box incorporating a scanning unit and a transfer box in which a photosensitive material sheet is exposed in the manner of a scanning to a slit-like light image from the exposure box. The exposed photosensitive material is superimposed on an image receiving material, then the image recorded on the photosensitive material is transferred to the image receiving material. The exposure box is put on the transfer box, and these boxes are located in position and secured by means of pins.
In the case of this duplicating camera, it is necessary to completely match the scan axis of the scanning unit with the axis along which the photosensitive material is conveyed in order to precisely transfer the image of the original to the image receiving material. If the scan direction of the scanning unit is at an angle to the direction in which the photosensitive material is conveyed, the resultant transferred image will be distorted into a parallelogram-like shape. Therefore, the exposure box and the transfer box are accurately positioned and fixed together.
Although these boxes are positioned by means of the pins as mentioned above, merely inserting the pins provided on the transfer box into the counterpart pin holes on the exposure box may cause the scan direction of the scanning unit in the exposure box to be at an angle to the transfer direction of the photosensitive material in the transfer box because of unevenness in position of the pins and pin holes.
In this type of duplicating camera, an exposure stage is composed of an exposure table on which the photosensitive material is slidably conveyed and conveyor rollers disposed upstream and downstream of the exposure table, and slit-like images of the original are exposed to the photosensitive material on the exposure table. To obtain a precise and high resolution duplicated image without distorted rulings, the photosensitive material must be transferred while it remains close contact with the upper surface of the exposure table, and the photosensitive material must remain flat. For these reasons, for example, a suction apparatus is hitherto provided on the exposure table so that the photosensitive material can be sucked downwards so as to remain closely in contact with the exposure table during its transfer. This results in a camera having a complicated structure and being heavier.